Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 171138

Area Forecast Discussion
National Weather Service Goodland KS
538 AM MDT Sat Jun 17 2017

.SHORT TERM...(Today through Monday night)
Issued at 334 AM MDT Sat Jun 17 2017

Forecast issues will be chance of thunderstorms before the front
arrives, the strength of the winds behind the front, and the chance
of precipitation behind the front. SATELLITE showing zonal or
nearly zonal flow from the Pacific into North America. There is
some troughing in the eastern portion of the country with weak
ridging in the western portion. This is leaving the area in a west
northwest flow aloft.

At jet level...models started out fine. At mid levels...models were
close and reasonable but would give a slight advantage to the
Canadian and Gfs. At the surface it looks like the Nam is starting
the best at this time. The Nam, Gfs, and Sref appeared to be doing
the best on the low level thermal field.

Today/tonight...Complicated setup through this period. Initial
boundaries, dryline/old front look to move south and east of the
area before peak heating can take place. Lower dewpoints will be in
place across the area with higher moisture content/instability south
of our area because of the above boundary movement. It looks like
the main lift will come in with a much stronger cold front and a
secondary rather strong shortwave/mid level baroclinic zone behind
the front.

What makes this interesting and complicated that models differ on
the timing/position of incoming front and associated lift aloft. The
Gfs tends to be faster on both points. Majority of the output,
synoptic and high resolution, supports the slower arrival of the
front and associated lift. So adjusted the pops accordingly. The
highest pops will occur from late this afternoon through mid evening
before decreasing. Believe the Nam is overdoing instability due to
main instability shoved south and east before main lift arrives.

However, there is low instability. That along with negative theta-e
lapse rates and rather strong mesoscale lift supports keeping
thunderstorms in through the evening before becoming
showers/embedded thunderstorms after midnight.

This appears to be a rather strong front. Majority of the output
tightens up the gradient behind the front, near 10 mb from north to
south, plus they have rather high 3 hour pressure falls. As a result
there should be windy conditions around from late afternoon into mid
evening. Any precipitation falling during these strong winds could
enhance the winds. Day shift will have to watch these closely.

Sunday/Sunday night...Guidance continues to come in cooler and
current blend supports that well and made no changes. The winds do
become lighter during the night especially in the east. However, it
appears an incoming shortwave/baroclinic zone will increase the
cloud cover and keep the temperatures from falling too much.

Monday/Monday night...Ridging aloft builds in rather strongly during
this period with northwest flow aloft well established across the
area. Models keep some kind of cloud cover around in the northwest
flow aloft. Because of this did not feel confident in raising maxes
from what the blend gave me.

.LONG TERM...(Tuesday through Friday)
Issued at 218 AM MDT Sat Jun 17 2017

Northwest flow aloft continues on Tuesday with high pressure over
the desert southwest and an upper trough over the eastern half of
the country. Precipitation chances return in the afternoon when a
weak disturbance passes across the region.

The High Plains is placed under zonal flow on Wednesday and Thursday
as a couple of shortwaves travel along the Canadian border and
flatten the ridge to the west. With a more active pattern aloft and
moisture returning to the area, spotty shower and thunderstorm
chances are forecast through at least Thursday with a better chance
on Wednesday. Friday appears to remain dry during the day as cooler
air filters into the region.

Temperatures warm at the start of the extended with highs climbing
from the low/mid 90s on Tuesday to the mid/upper 90s on Wednesday.
Highs trend downward during the latter half of the work week,
cooling to the upper 80s to low 90s by Friday. Low temperatures are
generally from the upper 50s to upper 60s through the period.


.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 530 AM MDT Sat Jun 17 2017

Vfr conditions are expected through the period. For Kgld, through
early afternoon the winds will shift to the north and increase to
near 15 knots. Late in the afternoon a strong cold front is
expected to move through the site. Behind that front north winds
will increase to near 22 knots with gusts to 30 knots. Along and
behind this front thunderstorms are expected to be near the site.
Since it is toward the half way point of the period, and there is
uncertainty in timing/placement of thunderstorms, chose to handle
with a vcts through the evening hours. From late evening through
the end of the period the winds will be north near 14 knots.

For Kmck, north to northwest winds of 5 to 12 knots are expected
through late this afternoon. From late afternoon a cold front will
move through the site and increase the north winds to near 18
knots with gusts to near 26 knots. As with Kgld, thunderstorms
will be near the site from late afternoon into the late evening
hours. Since toward the half way point through the period and
uncertainty in timing/placement of thunderstorms, chose again to
handle with vcts. From late evening to the end of the period,
light northwest winds will occur.




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